5 ms·

Presumably using light from the laser. I forget the exact numbers, but the proposed laser is on the order of hundreds of gigawatts. Even at 4 ly away, there sho

Presumably using light from the laser. I forget the exact numbers, but the proposed laser is on the order of hundreds of gigawatts. Even at 4 ly away, there should still be appreciable illumination from Earth.

dekhn 10y ago
The calculations you need are in https://www.youtube.com/watch?v=sImBlq542TQ https://www.youtube.com/watch?v=sImBlq542TQ (his point is that lasers can be used for communications between solar systems, but the power calculations are similar for transport).
jsjohnst 10y ago
Hundreds of gigawatts!? To my knowledge, there's never been a laser remotely that powerful that can emit for any constant duration. The highest power laser [0] in the world currently is 2 petawatts and it can only fire for one trillionth of a second. Per the same article (not sure on validity) the entire world electricity usage is somewhere around 2 terawatts, so something producing a continuous 0.1+ terawatt beam would be an incredible cost that's simply impractical proposition any time soon. [0] http://www.dailymail.co.uk/sciencetech/article-3179045/The-Death-Star-weapon-Japan-just-fired-world-s-powerful-laser.html http://www.dailymail.co.uk/sciencetech/article-3179045/The-D...
- unwind 10y ago
  I'm just jumping in here, but while we're in sci-fi land let me point out that this is usually not done from the Earth's surface (pushing 100 GW through the atmosphere is sub-optimal) but instead in near-Earth orbit, or from the Moon's surface, or something. So, the power output of the Earth is not 100% relevant, it wouldn't be a load on the planetary grid.
  - jsjohnst 10y ago
    Which makes it an even crazier proposition! The existing ultra high power lasers are so big in size that they'd currently be impractical bordering on implausible in space. To power it, we'd have to take every nuclear power plant on earth (plus another 2-3x more) and put them up in space. Seems likely, no? :P

dekhn 10y ago

The calculations you need are in https://www.youtube.com/watch?v=sImBlq542TQ https://www.youtube.com/watch?v=sImBlq542TQ (his point is that lasers can be used for communications between solar systems, but the power calculations are similar for transport).

jsjohnst 10y ago

Hundreds of gigawatts!? To my knowledge, there's never been a laser remotely that powerful that can emit for any constant duration. The highest power laser [0] in the world currently is 2 petawatts and it can only fire for one trillionth of a second. Per the same article (not sure on validity) the entire world electricity usage is somewhere around 2 terawatts, so something producing a continuous 0.1+ terawatt beam would be an incredible cost that's simply impractical proposition any time soon. [0] http://www.dailymail.co.uk/sciencetech/article-3179045/The-Death-Star-weapon-Japan-just-fired-world-s-powerful-laser.html http://www.dailymail.co.uk/sciencetech/article-3179045/The-D...

unwind 10y ago
I'm just jumping in here, but while we're in sci-fi land let me point out that this is usually not done from the Earth's surface (pushing 100 GW through the atmosphere is sub-optimal) but instead in near-Earth orbit, or from the Moon's surface, or something. So, the power output of the Earth is not 100% relevant, it wouldn't be a load on the planetary grid.
- jsjohnst 10y ago
  Which makes it an even crazier proposition! The existing ultra high power lasers are so big in size that they'd currently be impractical bordering on implausible in space. To power it, we'd have to take every nuclear power plant on earth (plus another 2-3x more) and put them up in space. Seems likely, no? :P